  //exports 导出单个成员
 var foo = 'bbb';
  // console.log(exports)
  exports.foo = 'hello';
  exports.add = function (x, y) {
    return x + y
  };
  exports.readFile = function (path, callback) {
    console.log('文件路径：', path)
  };

  var age = 18;
  exports.age = age;

  function add(x, y) {
    return x - y
  }
